Buoyant electric cable



Nov. 9, 1948. P. DuNsHEATH Erm. 2,453,418

BUOYANT ELECTRIC CABLE med Nov. so. 1940 z snmwnm 1 P07'5crv5w54r F PHAT/Varna@ Mausi/e 8 6 gnu/vaso caf/averne (Wvf/V CYL INDEB) Fig. 4. 5

Nov. 9, 1948. P. DUNsHl-:ATH ETAL BUOYANT ELECTRIC CABLE 2 Sheets-Sheet 2 Filed Nov. 30, 1940 a m W w www 4 y# Patented Nov. 9, '1948 UNITED STATES PATENT OFFICE BUoYAN'r ELECTRIC CABLE Percy Dunsheath, Abinger, and William Cyril Barry, Gravesend, England, asslgnors to W. T. Henleys Telegraph Works Company Limited, Westcott, Dorking, Surrey, England Application November 30, 1940, Serial No. 367,924

y In Great Britain January 4, 1940 c 25y claim. (ci. x14-101.5)

such purposes the cable must be rendered buoyant. It must also be ilexible and must possess sufllcient tensile strength to enable it t be trailed in considerable lengths without excessive deformation. It should offer as little friction as practicable and it should be capalble of giving up easily to the medium in which it floats the heat generated therein by the passage of the heavy current through the, cable. It is an object of this invention to provide a cable which satisiles these rather onerous requirements. According to our Vinvention we provide an insulated electric power cable comprising a flexible core which is extensively sub-divided longitudinally of the cable into a plurality of closed hollow cells suiilcing to render the cable buoyant in water, the cellular core comprising a series of resilient members with intercalations of relatively rigid members. The com- .bination of resilient members with relatively rigid members results in a core which is sufllciently flexible yet possesses adequate resistance to radial compression exerted, for instance, at a paying-out capstan and, in the case where the conductor is stranded or braided around the circumference of the core, due to the tension in the conductor. Either the resilient members or the rigid members or both resilient and rigid members may be of cellular form and the size of the closed hollow cells may vary very considerably according to the material or materials used for the manufacture of the core.

The cellular core may comprise a series of inflated spheres or cylinders of flexible material with intercalations of cylinders of relatively rigid material which may or may not be of cellular form. or it may comprise a series of cylinders of resilient cellular material, Yfor instance, soft expanded rubber, with intercal-ations of cylinders of relatively rigid cellular material, for instance, hard expanded rubber, cork or wood. The term cylinder is used herein in its broadest sense and where the context permits includes not only right circular cylinders but bodies having a surface approximating tothe cylindrical, cylindrical or approximately cylindrical surfaced bodies with concave or convex ends and such short cylindrical or approximately cylindrical bodies as might properly be termed discs. Alternatively the cellular core may comprise a series of resilient mem- 'bers with intercalations of hollow metal drums or of drums of moulded material, for instance, phenol formaldehyde resin or hard rubber. g

Generally, the cellular core will consist of a single chain of resilient and relatively rigid mem-` bers in cable in which the conductor is distributed around the circumference of the cellular core to facilitate the transfer of heat therefrom to the surrounding liquid. A single chain of elements may also be used in cable, such as a dredger cable, where the current is relatively small and the conductor may advantageously be located centrally within the core. In such a construction the elements of the chain will be of annular form and be threaded on the conductor, and may, if they are of insulating material, serve as a dielectric therefor. In some cases, however, the cellular core may be built up of a number of chains of resilient and relatively rigid members Ibunched or laid up helically together about the cable axis or disposed about. a central conductor which may be a solid or hollowstrand.4

The invention will now be more -fully described with the aid of the accompanying drawings which show, by way of example only, numerous constructions of cables with cellular cores built up of one or more series of resilient members with interoalations of relatively rigid members. f s

In the drawings Figure 1 is an elevation, partly in section, of the stepped end of a buoyant heavy current cable, employed for the detection and destruction of magnetically actuated submarine mines, with a cellular core, consisting of a series of inflated 'bodies with intercalations of cylinders o relatively rigid material; Y

vFigure 2 is a similar view of a buoyant heavy current cable with a modied form of the typ of cellular core shown in Figure 1;

Figure 3 is a similar view of ,a buoyant heavy current cable with a further modified form of the type of core shown in Figure 1;

Figure 4 is an elevation, partly in section, of the stepped-end of a buoyant heavy current cable with a cellular core consisting of a series of cylinders of resilient cellular material withintercalations of cylinders of relatively rigid cellular material;

Figure 5 -is an elevation of the stepped end of a buoyant powerA cable with a conductor located astenia within a cellular core of the type shown in Figure 4;,

Figure 6 is an elevation partly in section of the stepped end of a 'buoyant heavy current cable with a lcellular core consisting of a series of resilient members separated `by rigid hollow drums;

Figure 7 is an elevation partly in section of the stepped end of e. buoyant power cable with a central conductor located within a modliied form oi the type of core shown in Figure 6;

Figure 8 shows an elongated cavitied member suitable for use as a cellular core or as a ccmponent of a cellular core for a buoyant heavy current cable; and

Figure 9 showsI a buoyant power cable having a hollow conductor located within a group oi cavitled members of the type shown in Figure 8.

In the form of construction shown in Figure l the cellular core i consists of a series of resilient members 2 with a relatively rigid member 3 interposed between each two successive resilient members. The resilient members 2 are inflated cylinders oi rubber or rubber-like material and the relatively rigid members 3 are cylinders of wood of fairly low specific gravity, for instance, white pine, Such a construction has the advantage that both resilient and relatively rigid members are ci" -cellular form and both in themselves buoyant. Instead of wooden cylinders, cylinders of hard cellular rubber or of cori: may be used. The conducto-r fl is disposed about the cellular core and consists of an inner layer of wires stranded directly on the core and o an outer layer 6 of wires stranded in the opposite di. rection over a lapping 'i of tape applied to the first layer to prevent it bird-caging while the second layer is being applied. Over the tubular conductor so formed is a sheath d oitough rub ber which serves both as insulation for the conductor and as a waterproof protective sheath ior the cable. The construction of core i shown in Figure l is very resistant to radial compression and is, therefore, particularly suitable for the inboard end of a towed cable, It is not, however, so buoyant as the construction shown. in

Figure 2 in which the cellular core i is built up of groups of inflated members separated by relatively rigid short cylinders or discs i@ of wood. Each group of inflated members may comprise two o-r more hollow cylinders of rubber or other suitable flexible, impervious material but preferably three inilated members are used, acentral memberl iii inflated at a high pressure sandwiched between two members ii that are inflated at a lower pressure. With this arrangement the ends of the high pressure cylinder i@ embed themselves in4 the adjacent ends of the low pressure cylinders ill with the result that the cylindrical surfaces oi the three bodies are almost continuous, whereas il three cylinders inated to the same pressure are used the cylinders do not malte contact with one another save in the central parts thereof. The provision oi the high pressure cylinder in the centre of the group naturally gives greater support to the conductor l in the region it is most needed, namely intermediate the relatively rigid members i3. Although these latter members are shown to be of wood, they may be of hard expanded rubber, cork, or other suiciently rigid material. Their faces may be fiat, as shown, or they may b e dished the better to it against the bulged ends of the inilated cylinders on either side of them. The conductor carried by this form of cellular core may be similar to that described with reference to Figure l, but as an alternative it may, as shown, be built up of a number of separately insulated wires it, in which case it may be desirable to apply a wrapping ci rubber tape il@ to the circumierential suriace of each rigid member i3 to avoid the risk of damage to the insulation of the wires at these places. This form of conductor is particularly suitable in cases where the cellular core consists ci or includes expanded rubber which may be deleteriously affected by the high temperature to which the cable would be subjected during the pro-cess of vulcanlsng a rubber covering on the conductor. With a conductor built up o separately insulated-wires or strands it may be desirable to apply a waterproof protective sheath tov reduce friction during towing. Such a sheath is shown at ill and may be of a known kind not requiring the application of heat to an extent that may resuit in damage to the expanded rubber of the core.

In Figure 3 yet another form of cellular core built up of inated members is shown. In this form the resilient members are inilated spheres lli of rubber or lilre material and the relatively rigid members, of which one is sandwiched between each two spheres, are deeply dished discs it. These may be of wood, cellular rubber or cork, or they may be of some non-cellular but fairly light body, for instance, phenol formaldehyde resin. Over the cellular core l is disposed a conductor in the form of a tubular braid il' which is insulated and protected by a tough rubber sheath iii. It will be appreciated, however, that in place ol this braided conductor, a conductor ci the form shown in Figure l or in Figure 2, or a conductor of any other suitable form may be used with this form of cellular core. Similarly a braided con ductor may be combined with a cellular core oi the form shown in Figure l or Figure 2.

The inflated cylinders or spheres described with reference to Figures l, 2 and 3 may be produced in the same way as tennis balls. A hollow body is built up of a number of petals oi sheet rubber or the liire and before the body is closed up a quantity of a substance which on heating decomposes with evolution oi gas is introduced, The closed hollow body is placed in an appropriately shaped mould and heated. The pressure generated by the gas liberated from the substance forces the walls of the hollow body into Contact with the walls of the mould to form an inflated sphere or cylinder. The heating is continued until vulcanisation is complete.

Figure i shows an. example of a cable rendered buoyant by a cellular core i comprising a series of cylinders iii of resilient cellular material with intercalations of cylinders 2@ of relatively rigid cellular material. The former are preferably of soft expanded rubber and the latter of hard enpanded rubber, but, alternatively, the latter may well be of cork or wood. The cellular elements iQ oi the core l and also the cellular elements il@ may be cut from expanded rubber sheet and provided with a skin 2i of tough rubber to strengthen them and better enable them to support the surrounding conductor il, which is similar to that shown in Figure l and needs no further description.

Flgure 5 shows a cable in which the conductor 22 ls centrally disposed and insulated by a covering of rubber 22a and supported by buoyant elements of annular form threaded on the insulated conductor. These elements comprise resilient members 23 alternating with relatively rigid members 2t; the former are shown to be short cylinders or discs of soft expanded rubber and the latter cylinders of hard expanded rubber. The elements of the cellular core are enclosed in a 'waterproof protective covering of toughV rubber or the like. It will be apparent that the buoyant annular core may be built up of inflated spheres or cylinders and of rigid cylinders of the type described with reference to Figures 1-3 inclusive, provided they are formed with a central passage for the insulated conductor on which they are to be threaded.

A further form of cellular core is shown in Figure 6. It is built up of rigid hollow drums 2B of moulded material, .for instance, hard rubber or phenol formaldehyde resin, or o! metal, separated by resilientdiscs 21, for instance, discs of soit cellular rubber. 'I'he core is shown carrying a conductor 4 of the form shown in Figure 1, but this type of cellular core construction is also applicable to` cables embodying a central conductor, as will be clear from Figure 7 which shows a hollow conductor built up in a known manner of a single layer of wires 28 stranded about a support 29 consisting of an open helix of a strip of suitable cross-section, for instance, of channel, arcuate or circular cross-section, of metal or of hard non-metallic4 material such as hard rubber or synthetic plastic. The conductor is insulated by a covering 30 of suitable insulating material and on the insulated conductor are threaded alternately hollow drums 3| of annular form and annular discs 32 of resilient material.

In each of the examples of buoyant cable so. far described the cellular core I is built up of a plurality of separate members. some or all of which are of cellular form and some of which are resilient and others oi' which are relatively rigid, placed end to end. In the manufacture of such cable it is in most cases advantageous to connect the individual units together. This may be done in several ways, for instance. by uniting the central parts of the adjacent end faces of successive members by adhesive. Where the members are of rubber or alternately oi' rubber and wood, a coumarone resin-rubber adhesive is suitable. It may be advantageous so to build up the core ilrst in lengths of several fect and subsequently to join these lengths into long lengths. Alternatively, or additionally. the members may be connected together by a plurality of adhesive tapes 33 extending longitudinally of the core as shown in Figure 3 or by coverlng them with a light open 'braid 34 of cotton or other suitable material as shown in Figure 2. In cases where the cable conductor is built up on the cellular core, the units'of the core may be fed into the hollow conductor during the assem bly of the component wires. Where the units of the core are of annular form the core may be assembled by threading them on a cord or wire, or where the cable has a central conductor by threading them on the insulated conductor.

The core may, however, in certain cases be manufactured as an elongated cavitied member 35. A core of this form is shown in Figure 8 and comprises a plurality of large cells 38 having resilient rubber walls 31 separated by hard rubber discs 38 which are vulcanised to the end walls of the cells. Such a member may be made by alternately inserting in a tubular mould, first a disc of an unvulcanised or partially vulcanised hard rubber composition, then a hollow body oi' an unvulcanised soft rubber composition containing a quantity of asubstance which on heating decomposes with evolution of gas, then-'a ldisc of hard rubber composition, and so on. The composite body is then heated within the mould until vulcanisation is complete. Instead of employing a single cavitied body of this kind to formnthe core, the core may be built up of a number of such bodies bunched or laid up helically together aboutI the cable axis. or, as shown in Figure 9, disposed about a central conductor which may be a solid strand or,v as shown, a hollow conductor l0 formed by stranding the component wires about a cavitied member 4i similar to the members l5. The subject-matter disclosed in Figures 4 and 6 is claimed specifically in our copending application, Serial No. 713,319, flied November 30, 1946, as a division of this application and the subjectmatter disclosed in Figures 5, 7 and 8 is claimed specically in our copending application, Serial No. 713,320, also illed November 30, 1946, as a division of this application.

What we claim as our invention is:

1. In water-buoyant insulated electric power cable, a buoyancy element consisting' of a flexible cellular core comprising a series of resilient mem- ,bers with intercalations of relatively rigid members.

2. In water-buoyant insulated electric power cable. a buoyancy element consisting of a flexible cellular core comprising a series of inflated bodies of flexible material with intercalations of bodies of relatively rigid material.

3. In Water-buoyant insulated electric power cable, a buoyancy element consisting of a flexible cellular core comprising a series of inflated bodies of flexible material with intercalation's oi' cylinders of relatively rigid material.

4. In water-buoyant insulated electric power cable, a buoyancy element consisting of a flexible cellular core comprising a series of inflated bodies of flexible material and a plurality of buoyant cylinders of relatively rigid material intercalated in said series of inflated bodies.

5. In water-buoyant insulated electric power cable, a buoyancy element consisting of a. flexible cellular core comprising a series of inflated bodies of flexible material and a plurality of cylinders oi relatively rigid cellular material intercalated in said series of inflated bodies.

6. In water-buoyant insulated electric power cable, a buoyancy element consisting of a flexible cellular core comprising a series of inflated rubber bodies and a plurality of wooden cylinders intercalated in said series of inflated bodies.

7. In water-buoyant insulated electric Apower cable, a buoyancy element consisting of. a flexible cellular core comprising a series of groups of inflated rubber bodies and a plurality of relatively rigid members, each group of inflated bodies consisting of a body inflated at high pressure sandwiched between two bodies inflated at a lower pressure and adjacent groups being separated by at least one of said relatively rigid members.

8. In Awater-buoyant insulated electric power cable, a buoyancy element consisting of a flexible cellular core comprising low pressure inflated rubber cylinders and wooden cylinders, each two adjacent inilated cylinders being separated by a wooden cylinder.

9. In water-buoyant insulated electric power cable having a buoyancy element consisting of a flexible cellular core comprising a series oi resilient members with intercaiations of relatively rigid members, a plurality of adhesive tapes extending longitudinally of the coreand connecting the core members together.

i cellular core comprising a series of resilient members, relatively rigid members intercalated in said series of resilientI members, and an open tubular braid enclosing said resilient and said relatively rigid members.

11. In water-buoyant insulated electric power cable, a buoyancy element in the form ot an elongated cellular member built up of a series ot resilient members with relatively rigid members intercalated in said series of resilient members.

l2. In water-buoyant insulated electric power cable having a conductor comprising a plurality oi wires laid helically about a core comprising a plurality of short buoyancy elements oi' resilient material. the inclusion in said core of a plurality of relatively rigid members distributed along the length thereof, whereby to increase the resistance oi said cable to crushing.

13. In water-buoyant insulated electric power cable, a buoyancy element consisting of a flexible core comprising a series of resilient members with intercalations of relatively rigid members of substantially the same overall diameter as said resilient members.

14. In water-buoyant insulated electric power cable, a buoyancy element consisting of a substantially cylindrical core built -up of a series oi resilient members and of relatively rigid members intercalated in said series.

15. In water-buoyant insulated electric power cable, a buoyancy element in the form oi an elongated member built up oi hollow cylinders and solid cylinders, the cylinders of one type being of flexible material and the cylinders of the other type being of relatively rigid material.

16. In water-buoyant insulated electric power cable, at least one buoyancy element in the form of an elongated cavitied member consisting of inflated cells with flexible walls separated from one another by cylinders of relatively rigid material.

17. In water-buoyant insulated electric power cable, at least one buoyancy element in the form of an elongated cavitied member consisting of inflated cells with iiexible walls of an cylinders ci relatively rigid material, the end faces of adjacent components parts of the member being united by adhesive.

18. In water-buoyant insulated electric power cable, a buoyancy element consisting of a flexible cellular core comprising a series of iniiated rubber bodies, a plurality of relatively rigid members intercalated in said series of inflated bodies, and means comprising a number o adhesive tapes extending longitudinally o the core for connecting together said inflated rubber bodies and said rigid members.

19. In water-buoyant insulated electric power cable, a buoyancy element consisting o! a ilexible cellular core comprising low pressure iniiatedrubber bodies and wooden cylinders arranged alternately and means consisting of a number of adhesive tapes extending longitudinally of the core for connecting said cylinders together.

20. In water-buoyant insulated electric power cable. a buoyancy element consisting of a flexible cellular core comprising a series yot resilient members with intercalations oi' relatively rigid members, the adjacent end faces of the individual core members being united together by adhesive.

21. A water-buoyant insulated electric power cable, having a flexible cellular core comprising a series of cylinders of resilient material and a plurality of cylinders ot relatively rigid material intercalated in said series o! cylinders oi resilient material, and a conductor oi' hollow form enclosing said core comprising a plurality o! component wires wound helically around said core.

22. In water-buoyant insulated electric power cable, a buoyancy element in the form o! an elongated member built up of a series o! resilient spherical members and o! `relatively rigid members intercalated in said series.

23. In water-buoyant insulated electric power cable, a buoyancy element in the form of an elongated member built up o! a series oi inflated spheres of resilient material and of relatively rigid members intercalated in said series.

24. In water-buoyant insulated electric power cable, a buoyancy element in the form o! an elongated member built up ot a. seriesof resilient 4 members and oi cylinders oi relatively rigid mate rial, having dished end faces, intercalated in said series.

25. In water-buoyant insulated electric power cable, a buoyancy element in the form of an elongated member consisting of inilated balls with ilexible walls separated from one another by deeply dished discs of water-buoyant. relatively rigid material,

PERCY DUNSHEATH. WILLIAM CYRIL BARRY.

REFERENCES CITED The following references are oi' record in the file or" this patent:

UNITED STATES PATENTS Number Name Date 2,048,311 Peirce July 28, 193B FOREIGN PATENTS Number Country Date ifiiliiiifi Germany Nov. 18, 1934 

